Help with IMPCO Tank Plumbing

[BMANN]

Hi All,
New guy here. I like to tinker with autos. A friend and I bought an old Crown Vic dedicated CNG to experiment with. The tank is damaged, but works so we got it cheap. I don't trust the tank so we bought a used IMPCO tank with bracket that is in great shape and has about 6 years left. Problem is, we have no idea what the different ports are on the electric valve and which electric connection goes where. I think the tank came from a Cavalier is why I'm posting the thread here.

There are four ports looking at the valve from the end. One pointing up appears to be a 3/8" Swagelok tubing connection. Then there are three VCO type o-ring face seal fittings, one to the lower right, one to the lower left and one pointing down. There are two wiring connections, one black socket with two wires and one gray socket with two wires.

Any help with identifying ports and wiring would be appreciated. We would like to get it hooked up and then have it inspected before trying to fill it and drive it. Thanks.

[siai47]

Re: Help with IMPCO Tank Plumbing

If you have a Cavalier HPL the ports are as follows: Looking at the valve it is a hex shape--four of the flats have fittings, two do not. There is also a brass vent valve on the face of the HPL. Directly above the vent valve is the port for the tank pressure sensor. Going clockwise around the valve the next flat is the fuel fill port, the next flat is blank, the next flat has a line that connects to vent the PRD (pressure relief device), the next flat is blank, the final flat is the high pressure outlet. There should be two electrical connectors on the valve. The one with a pink and light blue wire controls the H.P. lockoff valve solenoid. The one with a gray and dark blue wire goes to the internal fuel temperature sender. You need to provide a check valve on the fuel fill line between the HPL and the fill nozzle--in this setup when the HPL is energized, tank pressure appears at all ports except the PRD. Hope this helps .

[siai47]

Re: Help with IMPCO Tank Plumbing

One more thing (or a couple) . The black connector is the solenoid connector and the grey connector is the fuel tank temperature connector. The pink lead on the solenoid connector goes to +12 volts (fused no more than 10 amps, the light blue lead is gounded (in the Cavalier) by the ECU to open the fuel valve. The temperature sensor won't be of any use to you, but if you want to try, it needs to be fed by +5 volts on the gray lead and then connected via the dark blue lead to a digital volt meter to get the fuel temp. There is a chart in the Cavalier manual that shows the temp to voltage relationship of the sensor. If you want to keep the connectors, they are 2-way F Metri-pack sealed 150 series (available at you Chevy dealer, major junkyards, etc.) or butt splices available at Home Depot--your choice . You will need to cap the port that had the pressure sensor installed.

[BMANN]

Re: Help with IMPCO Tank Plumbing

Fantastic! I knew someone had experience with these. Sure beats trial and error. A great big thanks for the information. The only thing that is different on this valve is that the wire leads going to the connectors are black and white, both on the RTD tank temperature connector and the solenoid connector (no pink lead). Do you know which one is +12v and which is ground on the solenoid? I would normally assume the black is the ground, but you never know.

Two more question, is the pressure relief valve integrated into the tank valve (just route pressure relief port to the outside), or do I need to supply my own pressure relief valve to the port? Also what was the original GGE volume rating on these tanks?

[siai47]

Re: Help with IMPCO Tank Plumbing

The PRD is in the lockoff valve. The line just needs to exit the vehicle interior to vent fuel if necessary. As far as the solenoid connection---either wire is fine for ground or power. Wire colors have changed over the model years and which wire (A or B) in the connector is hot has also changed. In the exterior wiring on the Cavalier there is a small diode across the coil of the solenoid to prevent voltage spikes from damaging whatever you are going to use to control the valve. You might consider adding one to your circuit. Usefull tank Capacity is around 5.5 GGE.